Two British science fiction enthusiasts, Graeme and Clive, embark on a road trip across the United States to visit famous UFO hotspots and attend Comic-Con in San Diego. Along the journey, a chance encounter leads them to an alien named Paul, who has escaped from a top-secret military base. Paul, with his crude humor and laid-back attitude, quickly befriends the duo. He reveals that he has been held captive for over 60 years and seeks their help to reach a rendezvous point where he can be rescued by his mothership. Despite initial shock and hesitation, Graeme and Clive decide to assist Paul in his quest for freedom.

As the trio travels across the country, they are pursued by federal agents intent on recapturing Paul and an obsessive father who believes the alien abducted his daughter. Along the way, Graeme and Clive confront their fears, deepen their friendship, and experience a series of misadventures. Their journey is filled with comedic escapades and challenges that test their resolve and ingenuity. The film expertly balances humor with heartfelt moments, creating a memorable road trip adventure that explores themes of friendship, acceptance, and the quest for freedom.